In 1987 Garrett was involved in Michael Jackson's Badalbum, singing a duet with Jackson on "I Just Can't Stop Loving You" in several different languages (among which were French and Spanish). She co-wrote the #1 single "Man in the Mirror". In a 2013 interview with Luka Neskovic, Garrett said: "All I wanted to do was give Michael something he would want to say to the world, and I knew it couldn't be another 'Oh baby, I love you' song. It had to be a little bit more than that. It needed to have some substance. He hadn't recorded anything like this to that point. I was just taking the risk that he might not get it, you know. First of all, I need to send it through Quincy because if Quincy didn't like it there is no way that Michael would've ever heard it. It was a huge privilege for me when Quincy decided that the song was good enough to play for Michael."[2]

Garrett and Jackson recorded a Spanish version of "I Just Can't Stop Loving You", titled "Todo Mi Amor Eres Tu" (loosely translated to "All My Love Is You").[3] Also now available is a French version titled "Je Ne Veux Pas La Fin De Nous" which was also recorded during the same recording sessions for the "Bad" album. A gifted musical sight reader with perfect vocal pitch (as most session vocalists are), the initial duet for "I Just Can't Stop Loving You" came as a total surprise to Garrett who simply answered the call expecting to only appear as a background vocalist. She initially felt intimidated with excitement when she entered the recording booth and noticed two music stands with sheet music that had lyric parts labeled "Michael" and "Siedah."

Garrett's association with Jackson enabled her to sing on several Quincy Jones albums of the 1980s and 1990s, co-writing his hit songs "Tomorrow (A Better You, Better Me)", "Back On The Block," and "The Secret Garden (Sweet Seduction Suite)" Garrett also toured with Michael Jackson from 1992 to 1993 on his Dangerous World Tour, singing backing vocals and duetting with him for "I Just Can't Stop Loving You". In the Dangerous album, Garrett also wrote a song "Keep the Faith" with Michael Jackson and Glen Ballard, the co-songwriter of Man in the Mirror. She appears in the concert film "Michael Jackson Live in Bucharest: The Dangerous Tour."

In addition, Garrett's 1988 solo album Kiss Of Life includes "Baby's Got It Bad", a version of Jackson's "Got The Hots" with rewritten lyrics. "Got The Hots" was an unreleased track from the Thriller sessions at the time, but has since been released.

In 1991, she became host of the show America's Top 10. In 1995 Garrett was also involved with Maysa Leak's (of the group Incognito) solo debut album as co-writer of the track "Sexy" in which she also sang backing vocals.

In 1996 she joined the Brand New Heavies, collaborating on just one album, 1997's Shelter. As part of the band, she co-wrote their top 5 hit "Sometimes" and enjoyed a minor hit with a cover of Carole King's "You've Got A Friend". Garrett left the group in early 1998 to concentrate on her own songwriting. In 1997, she wrote "Be Good or Be Gone" for Edyta Górniak.

Garrett supported Madonna as a backing singer and dancer on The Re-Invention Tour in 2004. Garrett's professional involvement with Madonna goes back some years as she previously supplied backing vocals on some of Madonna's earlier material including True Blue (1986), and Who's That Girl (1987).

Garrett co-wrote four songs for the 2011 film Rio, where she is also a featured artist on the soundtrack on the song "Funky Monkey". The song "Real In Rio" (co-written by Garrett, Sergio Mendes, and Carlinhos Brown) was nominated for an Oscar for Best Original Song.

In 2011, she appeared on American Idol singing with contestants Haley Reinhart, and most notably Jacob Lusk, with whom she sang her song "Man in the Mirror". (Air date 04/06/2011)[4]

Garrett's latest single, "Keep On Lovin' You", a tribute to Michael Jackson and an answer to their duet IJCSLY, was made available on iTunes September 11, 2012.

↑ Young, John (April 7, 2011). "'American Idol' behind the scenes: 'Idol' coaches talk the Top 9 -- EXCLUSIVE". Entertainment Weekly. Retrieved April 7, 2011. He (Jacob Lusk) was also very excited to have [the song’s co-writer] Siedah Garrett on stage with him. That added an extra element — that he could walk over and sing a portion of this song with her. Siedah delayed her flight to Malaysia to do Idol. It was an extremely expensive ticket to change, because she was doing a corporate gig in Malaysia. But she wouldn’t miss this opportunity to save her life.